The electric motor described in, for example, Japanese Unexamined Patent Publication No. 2013-240215 has been known as such electric motor.
The electric motor described in Japanese Unexamined Patent Publication No. 2013-240215 has a rotor, a stator provided around the rotor, a housing for storing the rotor and the stator, a lead wire connected electrically to the stator, a partition wall that separates a sealing space for injecting a sealant into the housing and a space outside the sealing space from each other and allows the lead wire to be extended to the outside of the sealing space, and a cover that is attached to the housing and the partition wall.
The housing has an opening for opening a storage space to one side of an axial direction along the central axis of rotation of the rotor, the storage space storing the rotor and the stator. A notch that is concaved from an edge surface surrounding this opening toward the other side of the axial direction is formed in the housing.
The partition wall is made from an elastic member (such as silicone rubber) and inserted into the notch of the housing. A through-hole into which the lead wire is inserted is formed in the partition wall.
The cover is attached to the housing and the partition wall while in contact with the edge surface surrounding the opening of the housing (the storage space) and an end surface of the partition wall in order to close the opening of the housing.
The electric motor described in Japanese Unexamined Patent Publication No. 2013-240215 is manufactured as follows.
The stator is inserted into a predetermined position inside the housing that has the partition wall attached beforehand.
The lead wire connected to the stator is inserted into the through-hole of the partition wall, and then the partition wall is inserted into the notch of the housing.
An injection mold is mounted onto the housing and the partition wall from one side of the axial direction. This brings the injection mold into contact with the edge surface of the housing and the end surface of the partition wall, creating the sealing space for injecting the sealant, between the injection mold, the housing, and the partition wall.
In this condition, the sealant is injected into the sealing space through the injection mold.
In some cases, the sealant is injected, with the cover mounted on the housing and the partition wall rather than the injection mold.
However, the fact that the partition wall is made from an elastic member creates a risk that the partition wall might elastically deform under pressure of the sealant upon injection thereof, causing the sealant to leak to the outside of the housing through between the partition wall and the housing or the injection mold (or the cover).
Although a metal partition wall can be used as another example of the partition wall as described in Japanese Unexamined Patent Publication No. 2013-240215, use of a metal partition wall makes it difficult to align the position of the edge surface of the housing and the position of the end surface of the partition wall along the axial direction. Misalignment of these surfaces creates a risk that the sealant might leak from between the housing, the partition wall, and the injection mold or the cover during the injection of the sealant.